diff --git a/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/6_4_0/4526-fix-reduction-step.yaml b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/6_4_0/4526-fix-reduction-step.yaml
new file mode 100644
index 00000000000..81ed230ca2c
--- /dev/null
+++ b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/6_4_0/4526-fix-reduction-step.yaml
@@ -0,0 +1,7 @@
+---
+type: fix
+issue: 4526
+title: "Fixing an issue where a long running reduction step causes
+      the message not to be processed fast enough, thereby allowing
+      multiple reduction step jobs to start.
+      "
diff --git a/hapi-fhir-storage-batch2/src/main/java/ca/uhn/fhir/batch2/coordinator/WorkChannelMessageHandler.java b/hapi-fhir-storage-batch2/src/main/java/ca/uhn/fhir/batch2/coordinator/WorkChannelMessageHandler.java
index a8fa8a00d25..1920ef0a372 100644
--- a/hapi-fhir-storage-batch2/src/main/java/ca/uhn/fhir/batch2/coordinator/WorkChannelMessageHandler.java
+++ b/hapi-fhir-storage-batch2/src/main/java/ca/uhn/fhir/batch2/coordinator/WorkChannelMessageHandler.java
@@ -36,6 +36,7 @@ import ca.uhn.fhir.batch2.util.Batch2Constants;
 import ca.uhn.fhir.rest.server.exceptions.InternalErrorException;
 import ca.uhn.fhir.util.Logs;
 import org.apache.commons.lang3.Validate;
+import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHandler;
@@ -43,6 +44,9 @@ import org.springframework.messaging.MessagingException;
 
 import javax.annotation.Nonnull;
 import java.util.Optional;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ThreadFactory;
 
 /**
  * This handler receives batch work request messages and performs the batch work requested by the message
@@ -112,7 +116,27 @@ class WorkChannelMessageHandler implements MessageHandler {
 		}
 
 		JobStepExecutor<?,?,?> stepExecutor = myJobStepExecutorFactory.newJobStepExecutor(instance, workChunk, cursor);
-		stepExecutor.executeStep();
+		// TODO - ls
+		/*
+		 * We should change this to actually have
+		 * the reduction step take in smaller sets of
+		 * lists of chunks from the previous steps (one
+		 * at a time still) and compose the
+		 * report gradually and in an idempotent way
+		 */
+		if (isReductionWorkNotification) {
+			// do async due to long running process
+			// we'll fire off a separate thread and let the job continue
+			ScheduledExecutorService exService = Executors.newSingleThreadScheduledExecutor(new ThreadFactory() {
+				@Override
+				public Thread newThread(@NotNull Runnable r) {
+					return new Thread(r, "Reduction-step-thread");
+				}
+			});
+			exService.execute(stepExecutor::executeStep);
+		} else {
+			stepExecutor.executeStep();
+		}
 	}
 
 	private void markInProgressIfQueued(JobInstance theInstance) {